The purpose of this project is to clarify the role of microtubules and microfilaments in cell motile processes by filling some of the gaps in our understanding of their structure and function. Urodele neurulation would be used as a model system. I propose to examine some aspects of the behavior of paraxial microtubules during elongation of neural plate cells by 1) looking for evidence of microtubule-dependent directed transport during elongation of isolated single cells, 2) ascertaining whether protein synthesis is required for elongation, an 3) using the high voltage electron microscope to describe microtubule distribution and to perform a morphological assay for a possible pool of microtubule subunits induced to polymerize with D2O (this assay might also indicate sites of addition of new subunits). Microfilament bundles encircle the apices of neural plate cells. These cells undergo apical constriction as the plate rolls up to form the neural tube. I propose to study the structure and function of apical microfilaments by 1) composing a complete map of the morphology and distribution of microfilaments at early and late stages of constriction from serial sections and high-resolution studies employing special preparative procedures 2) isolating sheets of apical microfilament network for study with negative staining, 3) describing the polarity of individual microfilaments within the bundles by means of HMM binding, 4) attempting to induce constriction in glycerinated models of neural plates and in isolated microfilament networks, and 5) using a technique for induction of microfilaments in combination with protein synthesis inhibition to assay for a pool of microfilament precursors.